1. Field of the Invention
The present invention relates to a process through which an intimate bonding between latex foam materials and certain rigid materials can be produced, as well as to parts formed by this process.
2. Description of the Background
Foam materials are employed for many purposes such as for upholstered furniture, mattresses, and many other applications in the furniture industry; for the interiors of vehicles in the automobile industry; for pipe insulation and sound deadening materials in the building industry; and in many other fields. It is frequently difficult, however, to install foamlike elastic materials or to combine them with rigid thermoplastic materials. Up to this time, adhesives have been used, or attempts have been made to achieve a certain adhesion with mechanical stapling or notching. In such cases a thermoplastic structural material, of such form as injection molded, extruded, blow molded pressed, laminated or otherwise produced plastic components is used.
Surprisingly, it has now been found that by using certain thermoplastic structural materials during the vulcanization process, an intimate bonding is produced between a latex foam material and the thermoplastic structural material. In this manner stable foam-plastic composite articles can be produced in one step.
Composite articles of thermoplastics and rubber are well known. Thus, EP-A-O 196 407, for example, describes a process for producing a combination between plastic compositions based on polyphenylene ethers, on one side, and sulfur-vulcanized rubbers containing double bonds on the other. In this case, the rubbers contain filling materials and plasticizers. The co-vulcanization, however, is successful only when it is carried out at temperatures between 140.degree. and 200.degree.. Of course the polymer compositions must show a correspondingly high heat deflection temperature under load, which severely restricts their composition and in addition requires difficult processing. The use of latex rubber for this process appeared to promise little success. It is not only to be expected that the water present as a third phase would disturb co-vulcanization, but above all the limitation of the temperature for co-vulcanization to a maximum of about 100.degree. C. appears to be prohibitive. For these reasons the formation of a stable combination is not expected.